The present invention concerns dish-electrode concentration meters and their transducers, and specifically those employed to measure the concentration of a substance of interest, usually a gas, in blood. The transducer of the meter adjoins a structure which defines a small dish, the bottom of which is formed by the transducer structure itself, and one or perhaps two drops of blood are dropped into the dish for contact with the concentration meter's actual transducer. The amount of blood involved in such a measurement is very small, on the order of about 20-50 microliters. The structure defining the little dish or pan is typically made of good thermally conductive material and is furthermore in good thermally conductive engagement with the actual transducer, in order that both the one or two drops of blood contacting the transducer and also the transducer be capable of being maintained at the temperature at which the concentration measurement need be performed.
Such a dish-electrode concentration meter is disclosed, for example, in Federal Republic of Germany published patent application DE-OS No. 23 47 779. With such constructions, the heating element, e.g., a heating coil, of the thermostatic system used to maintain required temperature is mounted on the actual transducer structure, as is also the temperature sensor of the meter's thermostatic system. There is a frequent need to replace the transducer of the concentration meter, for various reasons including wear, the need for inspection, and so forth. However, removal of the transducer then necessitates removal or disassembly of the heating element and the temperature-sensing element of the meter's thermostatic system; alternatively, the temperature sensor is non-removably mounted on the transducer structure, or is not feasably disassembled from the transducer structure, so that when the new or substitute transducer is then installed it is accompanied by a new temperature sensor whose presence, in turn, necessitates recalibration.